A triangular crawler device in construction equipment will be explained with FIG. 1. A revolving superstructure 3 is mounted on a body 2 of construction equipment 1. A working machine 4 having a bucket or the like, a driver's cab 5, an engine compartment 6, and the like are attached to the revolving superstructure 3. The body 2 is provided with triangular crawler devices 7 which are travel devices. Specifically, a pair of rear triangular crawler devices 7A on opposite sides, each having a driving element, are disposed at the rear portion of the vehicle 2, and a pair of front triangular crawler devices 7B on opposite sides, each having a driving element and a steering device, are disposed at the front portion of the vehicle 2.
An example of such triangular crawler devices as above is described in Japanese Patent Laid-open No. 4-8682. Specifically, a track frame, including a front idler and a rear idler at the front and rear ends thereof respectively, is rotatably attached to a sprocket axle via a bearing. A crawler belt is wound around the outer peripheries of the sprocket and the front and rear idlers, and forms a triangular shape. Thus, when the vehicle travels on rough ground, the track frame rocks with the sprocket axle as a center following the lay of the ground, which reduces the rocking of the vehicle.
However, the above configuration has a disadvantage in that the front portion of the front triangular crawler device 7B does not always turn upwardly but can turn downwardly, depending on conditions, to thereby cause it to stumble when the front idler collides with an obstacle in front while the vehicle travels.